/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.io;



import com.bff.gaia.unified.sdk.io.fs.ResourceId;

import com.bff.gaia.unified.sdk.options.ValueProvider;

import com.bff.gaia.unified.sdk.util.MimeTypes;



import javax.annotation.Nullable;

import java.io.IOException;

import java.io.OutputStreamWriter;

import java.nio.channels.Channels;

import java.nio.channels.WritableByteChannel;

import java.nio.charset.StandardCharsets;



/**

 * Implementation detail of {@link TextIO.Write}.

 *

 * <p>A {@link FileBasedSink} for text files. Produces text files with the newline separator {@code

 * '\n'} represented in {@code UTF-8} format as the record separator. Each record (including the

 * last) is terminated.

 */

class TextSink<UserT, DestinationT> extends FileBasedSink<UserT, DestinationT, String> {

  @Nullable

  private final String header;

  @Nullable

  private final String footer;

  private final char[] delimiter;



  TextSink(

      ValueProvider<ResourceId> baseOutputFilename,

      DynamicDestinations<UserT, DestinationT, String> dynamicDestinations,

      char[] delimiter,

      @Nullable String header,

      @Nullable String footer,

      WritableByteChannelFactory writableByteChannelFactory) {

    super(baseOutputFilename, dynamicDestinations, writableByteChannelFactory);

    this.header = header;

    this.footer = footer;

    this.delimiter = delimiter;

  }



  @Override

  public WriteOperation<DestinationT, String> createWriteOperation() {

    return new TextWriteOperation<>(this, delimiter, header, footer);

  }



  /** A {@link WriteOperation WriteOperation} for text files. */

  private static class TextWriteOperation<DestinationT>

      extends WriteOperation<DestinationT, String> {

    @Nullable

	private final String header;

    @Nullable

	private final String footer;

    private final char[] delimiter;



    private TextWriteOperation(

		TextSink sink, char[] delimiter, @Nullable String header, @Nullable String footer) {

      super(sink);

      this.header = header;

      this.footer = footer;

      this.delimiter = delimiter;

    }



    @Override

    public Writer<DestinationT, String> createWriter() throws Exception {

      return new TextWriter<>(this, delimiter, header, footer);

    }

  }



  /** A {@link Writer Writer} for text files. */

  private static class TextWriter<DestinationT> extends Writer<DestinationT, String> {

    private static final String NEWLINE = "\n";

    @Nullable

	private final String header;

    @Nullable

	private final String footer;

    private final char[] delimiter;



    // Initialized in prepareWrite

    @Nullable

	private OutputStreamWriter out;



    public TextWriter(

        WriteOperation<DestinationT, String> writeOperation,

        char[] delimiter,

        @Nullable String header,

        @Nullable String footer) {

      super(writeOperation, MimeTypes.TEXT);

      this.delimiter = delimiter;

      this.header = header;

      this.footer = footer;

    }



    /** Writes {@code value} followed by a newline character if {@code value} is not null. */

    private void writeIfNotNull(@Nullable String value) throws IOException {

      if (value != null) {

        writeLine(value);

      }

    }



    /** Writes {@code value} followed by the delimiter byte sequence. */

    private void writeLine(String value) throws IOException {

      out.write(value);

      out.write(delimiter);

    }



    @Override

    protected void prepareWrite(WritableByteChannel channel) throws Exception {

      out = new OutputStreamWriter(Channels.newOutputStream(channel), StandardCharsets.UTF_8);

    }



    @Override

    protected void writeHeader() throws Exception {

      writeIfNotNull(header);

    }



    @Override

    public void write(String value) throws Exception {

      writeLine(value);

    }



    @Override

    protected void writeFooter() throws Exception {

      writeIfNotNull(footer);

    }



    @Override

    protected void finishWrite() throws Exception {

      out.flush();

    }

  }

}